A method of measuring exercise intensity and energy expenditure of a physical activity using an acceleration sensor is known (see Patent Documents 1 and 2). In a device of Patent Document 1, a standard deviation Sw of acceleration at a constant time tw is calculated from an output signal of the acceleration sensor, and exercise intensity wi is calculated from the standard deviation Sw using a conversion formula prepared in advance. In a device of Patent Document 2, an impulse of an exercise mass is calculated by vector synthesis from the acceleration of three axes, and the energy expenditure is calculated from the impulse in correspondence to a type of exercise. The type of exercise is determined based on the ratio of the impulse by synthesized vector and the impulse in the front and back, left and right, and up and down directions.
[Patent Document 1] Japanese Unexamined Patent Publication No. 2006-204446
[Patent Document 2] Japanese Unexamined Patent Publication No. 2001-258870